Research On Synthesis And Electrochromic Properties Of DPP-type Conductive Polymers

Conductive polymer electrochromic materials have become a hotspot in the resear ch of the current due to their ease of structure design,rich color adjustable,easy pro cessing and many other advantages,At present,Electrochromic materials have made a series of achievements in the study of the theory of the polymer,structural design,o ptimization and the device.In order to achievelarge-scale industrial applications,develo pting high performance and good solubility electrochromic materials is still the researc h focus,especially on the selection anddesign of the donor and receptorunits.3,6-bis(5-bromothiophene-2-yl)-2,5-bis(2-octyldodecyl)pyrrole[3,4-c]pyrrole-1,4(2H,5H)-dione(DPP)structure containing lactam groups remain in a highly deficient sate of electrons condi tion.DPP is a very good receptor units in D-A type conducting polymersand the stud y of DPP kind of conductive polymers are mainly concentrated in the field of photov oltaic devices,in the field of electrochromism has not caused people's enough attentio n.So in this thesis we choose DPP as receptorsunit,eight kinds of conductive polymers was synthesized by the method of chemical polymerization,the experiment system co mpares the effect ofoptoelectronic propertiesof the D-A type and non D-A type structu re of conductive polymer and the effect of different donor units affect the performanc e of DPP kind of conductive polymers as well as the influence of different charge rat io of conjugate trimer.Thena series of characterization including photoelectric properties,electrochromic properties and thermal stability were studied.(1)(4,8-bis((2-octyldodecy)oxy)benzo[1,2-b:4,5-b']dithiophene-2,2-diyl)bis(trimetylstan nane)coupled with DPP and 4-(5,10-dibromo-1H-phenanthro[9,10-d]imidazol-2-yl)-N,Nbis(4-(hexyloxy)phenyl)aniline using Stille coupling polymerization to afford the D-A t ype polymer BEDPP and non D-A type polymer BTTPA,respectively.Through the test of polymer properties found that: BTDPP optical band gap of 1.40 eV,polymer color from dark blue to pale gray,color change is very obvious.While BTTPA optical ban dgap reached 2.38 eV,the color of the membrane is change from yellow to yellowish green to brown.The analysis of dynamics parameters can find BTDPP electrochromism performance is also better.Illustrates the structure of the D-A type can effectively reduce the polymer optical bandgap and improve material electrochromismperformance,fu rther prove to design D-A type structure is a effective meanto improve the electrochro mismperformance of polymer materials.(2)Using strong electron-withdrawing ability of the DPP as polymer receptor units,three different donor units(benzene,fluorene and carbazole).By Suzuki coupling reaction preparation of three kinds of different performance of conductive polymers,corresponding to BEDPP,FLDPP,CADPP.Findings: BEDPP optical band gap of 1.52 eV,the colour of the BEDPP film can shift from blue to CangQing when the film from a neutral state into oxidation state.FLDPP optical band gap of 1.68 eV,the colour of the FLDPPcan realize from blue to CangQing color shift when the film from a neutral state into oxidation state.CADPP optical band gap of 1.63 eV,the colour of the CADPP film can shift from blue to dark purple when the film from a neutral state into oxidation state.By comparing electrochromism parameters,We can find BEDPP and CADPP have more superior performance,they are good electrochromism materials.For FLDPP,it may be limitedin practical industrial applicationdue to its smaller optical contrast and response time is longer.So in the experiment we not only consider the donor for electronic ability strong and the weak,but also consider for donor receptor compatibility problems.(3)Three trimers were synthesizedthrough the coupling reaction polymerizationusing BDT,DTS and DPP,three kinds of monomers dosing raio of 4:3:1,3:2:1 and 2:1:1 respectively,corresponding to generate P1,P2 and P3 three kinds of polymer.In the experiment,we compare the different color,photoelectric properties and thermal stability of the trimers by adjusting the mol ratio of monomers attend the co-polymerization.The results show that in the three kinds of polymers P1,P2 and P3,the ability of the electron-donating gradually decreased with receptor unit ratio of DPP increase,initial oxidation potential increased gradually,at the same time the interaction between the donor and receptor gradually enhanced,reduced the band gap of polymer.Therefore,we can chang the photoelectric properties of the polymersby changing the mol ratio of monomers.Polymer P1 realizedcolor changes from dark purplein neutral states to CangQing in fulloxidation state.Polymer P2 realizedcolor change from violet in the neutral state to CangQingin completely oxidation state,polymer P3 realized from steel bluein neutral state to pale yellowin completely oxidation state.Either by changing different weight ratio,to change the color of the polymer.Overall,the electromic properties of polymer P1 are better than P2 and P3 both in visible and near-infrared light regions.However the thermal stability of the polymer P1 is poor,and may be limited to its further application.